FIGS. 1 and 2 show a device for measuring the absolute value of the density of salts in an atmosphere already invented by the inventor. In the FIGS., the reference numeral 1 designates an airtight water tank of a predetermined capacity which contains the super pure water 37 of a predetermined quantity, the resistivity of which is above 15M.OMEGA..cm. The tank 1 is made up of a material from which any dissolved material including sodium ions does not soak out, such as a transparent vinyl chloride. The numeral 2 designates a pipe for supplying the super pure water to the tank 1. The numeral 3 designates a valve provided at the pipe 2. The pipe 2 and the valve 3 constitute a means 30 for supplying the water. The numeral 5 designates a bubbling pipe for bubbling air in the atmosphere into the super pure water 37 in the tank 1 to dissolve the salts in the atmosphere into the super pure water 37. The numerals 4, 6, 8, 7, and 14 designate a pipe, a valve, a pump, a flow meter, and a timer, all of which constitute a means 40 for supplying air in the atmosphere to the bubbling pipe 5. The numerals 9 and 10 designate flow switches to hold the level of the super pure water 37 contained in the tank 1 at predetermined levels. The numeral 12 designates an exhaust pipe for exhausting the super pure water 37 contained in the tank 1 to the outside. The numeral 11 designates a valve provided at the exhaust pipe 12. The exhaust pipe 12 and the valve 11 together constitute a means 50 for exhausting the water. The numeral 13 designates a sodium ion analyzer for measuring the density of Na.sup.+ ions in the exhausted super pure water of a predetermined quantity. The material taking inlet or measuring tank 13a of the analyzer 13 is placed in the exhausted water.
The numeral 29 designates a bypass pipe for supplying super pure water at the water supplying means 30 to the material taking inlet 13a of the sodium ion analyzer 13 while bubbling through bypass. This bypass pipe 29 is located upstream of the water flow from the water tank 1 to the exhaust pipe 12 relative to the material taking inlet 13a. The numeral 31 designates a valve provided at the pipe 29. The pipe 29 and the valve 31 constitute a bypass means 70 for supplying super pure water through a bypass, and the bypass means 70 and the sodium ion analyzer 13 constitute a background value measuring means for measuring the density of sodium ions in the super pure water at the water supplying means 30 while bubbling occurs. The numeral 28 designates a pipe for supplying super pure water for washing the water tank 1, and the numeral 36 designates a valve provided at the pipe 28. The pipe 28 and the valve 36 constitute a means 60 for washing the water tank 1. The reference numeral 18 designates a mesh provided covering the outer surface of the cylindrical bubbling pipe 5. This mesh 18 can be provided inside the bubbling pipe 5.
The device will be operated as follows:
First, the valve 3 in the means 30 for supplying the water is opened, and the super pure water 37, the resistivity of which is above 15M.OMEGA..cm, is supplied to the airtight water tank 1 through the pipe 2. When the flow switch 9 operates, the valve 3 in the water supplying means 30 is closed to stop the supply of the super pure water 37 to the tank 1. Thus, the airtight water tank 1 is filled up with the super pure water 37 of a predetermined quantity. When the valve 6 in the means 40 for supplying air in the atmosphere is opened and the pump 8 is operated, air in the atmosphere is sent to the bubbling pipe 5 through the pipe 4 at a constant flow rate for a predetermined time. The bubbling pipe 5 operates to bubble the air into the super pure water 37 in the tank 1 to make the salts, that is, NaC1 in the air dissolved into the super pure water 37. When the bubbling is concluded, the valve 6 is closed, the valve 11 in the means 50 for exhausting the water is opened, and the super pure water in the tank 1 is exhausted to the outside through the pipe 12 at a constant flow rate caused by its positional potential. The sodium ion analyzer 13 with its material taking inlet 13a sunk placed in the exhausted super pure water operates to measure the density of Na.sup.+ ions in the super pure water. Then, the absolute value of the density of salts in the atmosphere is obtained from the density of Na.sup.+ ions in the super pure water measured by the sodium ion analyzer 13 by executing an operation including the mass-conversion between Na.sup.+ and NaCl.
Caused by the exhaustion of the super pure water, the flow switch 10 operates to open the valve 3, and thereafter, the above mentioned measuring operation is repeated. This enables continuous monitoring. In this case, the quantity of the air to be supplied is measured by the flow meter 7 and is regulated by the valve 6. The time period during when the air is supplied can be regulated by the timer 14. Furthermore, the time period during when the super pure water is supplied can be regulated by a means (not shown) provided in the water supplying means 30.
In the bubbling operation, the super pure water is supplied from the water supplying means 30 to the material taking inlet 13a of the sodium ion analyzer 13 at a predetermined flow rate by a bypass means 70 for supplying super pure water through a bypass, whereby the background value of the sodium ions, that is, the density of sodium ions in the super pure water before bubbling is measured by the sodium ion analyzer 5. After the super pure water to which air has been bubbled is exhausted, super pure water is supplied to the water tank 1 from above the tank 1 by the pipe 28 which is branched into two pipes inside the water tank 1, and the water tank 1 is washed thereby. By repeating the above-described operation, it is possible to measure and continuously monitor the absolute value of the salts in the atmosphere with a stable background value of sodium ions, resulting in a highly reliable measurement.
According to this device, a bypass means for supplying the super pure water to the sodium ion analyzer through a bypass is provided so as to stabilize the background value of the sodium ion analyzer, and a means for washing the water tank using the super pure water is provided so as to remove the remaining sodium ions in the tank. Such construction can provide a highly reliable result.
Furthermore, bubbles generated from the bubbling pipe 5 are minimized by the mesh 18, and therefore, the surface area ratio of the air and the super pure water contacting it is large. Furthermore, the velocity of the air supplied to the bubbling pipe 5 is controlled by the valve 6 and the flow meter 7 to be equal to that of the air flow outside the device. For example, when the device is installed outside, the above-mentioned velocity is made equal to the velocity of the outside air flow, and when the device is installed in a clean room which is ventilated, the velocity is made equal to the velocity of the air flow inside the room. This makes it possible to obtain a stable result regardless of changes of the state of the atmosphere, and it is especially effective for use in a region near the sea.
Furthermore, it is, of course, possible to control the quantity of air and the time period for bubbling depending on the density of salts in the atmosphere where the measurement is conducted. The sodium ion analyzer has a measuring range from 0.1 ppb to 1,000 ppb, and it may be provided with a function to output an alarm signal when the measured result exceeds the upper limit of the measuring range as a countermeasure against a high density of salts in a seaside region.
In this device, however, there is a disadvantage that the water in the tank 1 is contaminated by the oil mist of the pump 8 because air is supplied to the tank 1 from the outside by the pump 8. Furthermore, it is difficult to conduct a continuous monitoring because the valves are all manually operated.